Static and fatigue strength of composite plates with holes
Marek Barski
Quarterly No. 1, 2014 pages 3-7
DOI:
keywords: laminate, failure criteria, finite element method, stacking sequence optimization, damage, plate with hole
abstract The number of structures made from multi-layered composite materials increases every year. Some of these structures include different cutouts, which result from the manufacturing process or are needed for maintenance. This kind of discontinuities are the source of stress concentrations, which cause the nucleation and evolution of various forms of damages in composite materials. The problem of the damage becomes particularly important when the structure is subjected to cyclic loads. The present work concentrates on the investigation of the strength evaluation for rectangular composite plates with internal holes of different shapes. Numerical results are presented for circular, elliptic and square (with rounded corners) holes placed in the centre of a plate, which is subjected to bi-directional tension pressure imposed along the outer edges. It is assumed that the stacking sequence is symmetric with respect to the middle surface of the structure. The considered plates are made from an angle-ply laminate, which consists of the twelve layers with a fiber orientation angle ±θ, for example [±5°, ±5°, ±5°, ±5°]S, where 's' denotes the symmetry. The fiber orientation angle θ is studied in order to find the maximum strength of the considered plate. The solution is sought from the following discrete values, namely [0°, 5°, 10°, 15°, … , 90°]. The numerical calculations are performed with the use of the multipurpose finite element code ANSYS 12.1. In order to estimate the static strength of the structure, the linear (admissible stress) first ply failure criteria are applied. The influence of the geometry of the plate and the cutout on the optimal solution (fiber orientation angle ±θ) is also investigated. It is assumed that the ratio of the area of the analyzed plate and the hole is constant for the different shapes of holes. Simulations are performed for the two different materials, where the ratio of Young's modulus E1, E2 equal, respectively, E1/E2 << 1 (anisotropy) and E1/E2 ≈ 1 (quasi-isotropy).